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aio.c

/*
 *    An async IO implementation for Linux
 *    Written by Benjamin LaHaise <bcrl@kvack.org>
 *
 *    Implements an efficient asynchronous io interface.
 *
 *    Copyright 2000, 2001, 2002 Red Hat, Inc.  All Rights Reserved.
 *
 *    See ../COPYING for licensing terms.
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/aio_abi.h>
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/uio.h>

#define DEBUG 0

#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/aio.h>
#include <linux/highmem.h>
#include <linux/workqueue.h>
#include <linux/security.h>
#include <linux/eventfd.h>

#include <asm/kmap_types.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>

#if DEBUG > 1
#define dprintk         printk
#else
#define dprintk(x...)   do { ; } while (0)
#endif

/*------ sysctl variables----*/
static DEFINE_SPINLOCK(aio_nr_lock);
unsigned long aio_nr;         /* current system wide number of aio requests */
unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
/*----end sysctl variables---*/

static struct kmem_cache      *kiocb_cachep;
static struct kmem_cache      *kioctx_cachep;

static struct workqueue_struct *aio_wq;

/* Used for rare fput completion. */
static void aio_fput_routine(struct work_struct *);
static DECLARE_WORK(fput_work, aio_fput_routine);

static DEFINE_SPINLOCK(fput_lock);
static LIST_HEAD(fput_head);

static void aio_kick_handler(struct work_struct *);
static void aio_queue_work(struct kioctx *);

/* aio_setup
 *    Creates the slab caches used by the aio routines, panic on
 *    failure as this is done early during the boot sequence.
 */
static int __init aio_setup(void)
{
      kiocb_cachep = KMEM_CACHE(kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
      kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);

      aio_wq = create_workqueue("aio");

      pr_debug("aio_setup: sizeof(struct page) = %d\n", (int)sizeof(struct page));

      return 0;
}

static void aio_free_ring(struct kioctx *ctx)
{
      struct aio_ring_info *info = &ctx->ring_info;
      long i;

      for (i=0; i<info->nr_pages; i++)
            put_page(info->ring_pages[i]);

      if (info->mmap_size) {
            down_write(&ctx->mm->mmap_sem);
            do_munmap(ctx->mm, info->mmap_base, info->mmap_size);
            up_write(&ctx->mm->mmap_sem);
      }

      if (info->ring_pages && info->ring_pages != info->internal_pages)
            kfree(info->ring_pages);
      info->ring_pages = NULL;
      info->nr = 0;
}

static int aio_setup_ring(struct kioctx *ctx)
{
      struct aio_ring *ring;
      struct aio_ring_info *info = &ctx->ring_info;
      unsigned nr_events = ctx->max_reqs;
      unsigned long size;
      int nr_pages;

      /* Compensate for the ring buffer's head/tail overlap entry */
      nr_events += 2;   /* 1 is required, 2 for good luck */

      size = sizeof(struct aio_ring);
      size += sizeof(struct io_event) * nr_events;
      nr_pages = (size + PAGE_SIZE-1) >> PAGE_SHIFT;

      if (nr_pages < 0)
            return -EINVAL;

      nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring)) / sizeof(struct io_event);

      info->nr = 0;
      info->ring_pages = info->internal_pages;
      if (nr_pages > AIO_RING_PAGES) {
            info->ring_pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);
            if (!info->ring_pages)
                  return -ENOMEM;
      }

      info->mmap_size = nr_pages * PAGE_SIZE;
      dprintk("attempting mmap of %lu bytes\n", info->mmap_size);
      down_write(&ctx->mm->mmap_sem);
      info->mmap_base = do_mmap(NULL, 0, info->mmap_size, 
                          PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE,
                          0);
      if (IS_ERR((void *)info->mmap_base)) {
            up_write(&ctx->mm->mmap_sem);
            info->mmap_size = 0;
            aio_free_ring(ctx);
            return -EAGAIN;
      }

      dprintk("mmap address: 0x%08lx\n", info->mmap_base);
      info->nr_pages = get_user_pages(current, ctx->mm,
                              info->mmap_base, nr_pages, 
                              1, 0, info->ring_pages, NULL);
      up_write(&ctx->mm->mmap_sem);

      if (unlikely(info->nr_pages != nr_pages)) {
            aio_free_ring(ctx);
            return -EAGAIN;
      }

      ctx->user_id = info->mmap_base;

      info->nr = nr_events;         /* trusted copy */

      ring = kmap_atomic(info->ring_pages[0], KM_USER0);
      ring->nr = nr_events;   /* user copy */
      ring->id = ctx->user_id;
      ring->head = ring->tail = 0;
      ring->magic = AIO_RING_MAGIC;
      ring->compat_features = AIO_RING_COMPAT_FEATURES;
      ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
      ring->header_length = sizeof(struct aio_ring);
      kunmap_atomic(ring, KM_USER0);

      return 0;
}


/* aio_ring_event: returns a pointer to the event at the given index from
 * kmap_atomic(, km).  Release the pointer with put_aio_ring_event();
 */
#define AIO_EVENTS_PER_PAGE   (PAGE_SIZE / sizeof(struct io_event))
#define AIO_EVENTS_FIRST_PAGE ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
#define AIO_EVENTS_OFFSET     (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)

#define aio_ring_event(info, nr, km) ({                           \
      unsigned pos = (nr) + AIO_EVENTS_OFFSET;              \
      struct io_event *__event;                             \
      __event = kmap_atomic(                                \
                  (info)->ring_pages[pos / AIO_EVENTS_PER_PAGE], km); \
      __event += pos % AIO_EVENTS_PER_PAGE;                       \
      __event;                                        \
})

#define put_aio_ring_event(event, km) do {      \
      struct io_event *__event = (event); \
      (void)__event;                      \
      kunmap_atomic((void *)((unsigned long)__event & PAGE_MASK), km); \
} while(0)

/* ioctx_alloc
 *    Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
 */
static struct kioctx *ioctx_alloc(unsigned nr_events)
{
      struct mm_struct *mm;
      struct kioctx *ctx;

      /* Prevent overflows */
      if ((nr_events > (0x10000000U / sizeof(struct io_event))) ||
          (nr_events > (0x10000000U / sizeof(struct kiocb)))) {
            pr_debug("ENOMEM: nr_events too high\n");
            return ERR_PTR(-EINVAL);
      }

      if ((unsigned long)nr_events > aio_max_nr)
            return ERR_PTR(-EAGAIN);

      ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
      if (!ctx)
            return ERR_PTR(-ENOMEM);

      ctx->max_reqs = nr_events;
      mm = ctx->mm = current->mm;
      atomic_inc(&mm->mm_count);

      atomic_set(&ctx->users, 1);
      spin_lock_init(&ctx->ctx_lock);
      spin_lock_init(&ctx->ring_info.ring_lock);
      init_waitqueue_head(&ctx->wait);

      INIT_LIST_HEAD(&ctx->active_reqs);
      INIT_LIST_HEAD(&ctx->run_list);
      INIT_DELAYED_WORK(&ctx->wq, aio_kick_handler);

      if (aio_setup_ring(ctx) < 0)
            goto out_freectx;

      /* limit the number of system wide aios */
      spin_lock(&aio_nr_lock);
      if (aio_nr + ctx->max_reqs > aio_max_nr ||
          aio_nr + ctx->max_reqs < aio_nr)
            ctx->max_reqs = 0;
      else
            aio_nr += ctx->max_reqs;
      spin_unlock(&aio_nr_lock);
      if (ctx->max_reqs == 0)
            goto out_cleanup;

      /* now link into global list.  kludge.  FIXME */
      write_lock(&mm->ioctx_list_lock);
      ctx->next = mm->ioctx_list;
      mm->ioctx_list = ctx;
      write_unlock(&mm->ioctx_list_lock);

      dprintk("aio: allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
            ctx, ctx->user_id, current->mm, ctx->ring_info.nr);
      return ctx;

out_cleanup:
      __put_ioctx(ctx);
      return ERR_PTR(-EAGAIN);

out_freectx:
      mmdrop(mm);
      kmem_cache_free(kioctx_cachep, ctx);
      ctx = ERR_PTR(-ENOMEM);

      dprintk("aio: error allocating ioctx %p\n", ctx);
      return ctx;
}

/* aio_cancel_all
 *    Cancels all outstanding aio requests on an aio context.  Used 
 *    when the processes owning a context have all exited to encourage 
 *    the rapid destruction of the kioctx.
 */
static void aio_cancel_all(struct kioctx *ctx)
{
      int (*cancel)(struct kiocb *, struct io_event *);
      struct io_event res;
      spin_lock_irq(&ctx->ctx_lock);
      ctx->dead = 1;
      while (!list_empty(&ctx->active_reqs)) {
            struct list_head *pos = ctx->active_reqs.next;
            struct kiocb *iocb = list_kiocb(pos);
            list_del_init(&iocb->ki_list);
            cancel = iocb->ki_cancel;
            kiocbSetCancelled(iocb);
            if (cancel) {
                  iocb->ki_users++;
                  spin_unlock_irq(&ctx->ctx_lock);
                  cancel(iocb, &res);
                  spin_lock_irq(&ctx->ctx_lock);
            }
      }
      spin_unlock_irq(&ctx->ctx_lock);
}

static void wait_for_all_aios(struct kioctx *ctx)
{
      struct task_struct *tsk = current;
      DECLARE_WAITQUEUE(wait, tsk);

      spin_lock_irq(&ctx->ctx_lock);
      if (!ctx->reqs_active)
            goto out;

      add_wait_queue(&ctx->wait, &wait);
      set_task_state(tsk, TASK_UNINTERRUPTIBLE);
      while (ctx->reqs_active) {
            spin_unlock_irq(&ctx->ctx_lock);
            io_schedule();
            set_task_state(tsk, TASK_UNINTERRUPTIBLE);
            spin_lock_irq(&ctx->ctx_lock);
      }
      __set_task_state(tsk, TASK_RUNNING);
      remove_wait_queue(&ctx->wait, &wait);

out:
      spin_unlock_irq(&ctx->ctx_lock);
}

/* wait_on_sync_kiocb:
 *    Waits on the given sync kiocb to complete.
 */
ssize_t fastcall wait_on_sync_kiocb(struct kiocb *iocb)
{
      while (iocb->ki_users) {
            set_current_state(TASK_UNINTERRUPTIBLE);
            if (!iocb->ki_users)
                  break;
            io_schedule();
      }
      __set_current_state(TASK_RUNNING);
      return iocb->ki_user_data;
}

/* exit_aio: called when the last user of mm goes away.  At this point, 
 * there is no way for any new requests to be submited or any of the 
 * io_* syscalls to be called on the context.  However, there may be 
 * outstanding requests which hold references to the context; as they 
 * go away, they will call put_ioctx and release any pinned memory
 * associated with the request (held via struct page * references).
 */
void fastcall exit_aio(struct mm_struct *mm)
{
      struct kioctx *ctx = mm->ioctx_list;
      mm->ioctx_list = NULL;
      while (ctx) {
            struct kioctx *next = ctx->next;
            ctx->next = NULL;
            aio_cancel_all(ctx);

            wait_for_all_aios(ctx);
            /*
             * Ensure we don't leave the ctx on the aio_wq
             */
            cancel_work_sync(&ctx->wq.work);

            if (1 != atomic_read(&ctx->users))
                  printk(KERN_DEBUG
                        "exit_aio:ioctx still alive: %d %d %d\n",
                        atomic_read(&ctx->users), ctx->dead,
                        ctx->reqs_active);
            put_ioctx(ctx);
            ctx = next;
      }
}

/* __put_ioctx
 *    Called when the last user of an aio context has gone away,
 *    and the struct needs to be freed.
 */
void fastcall __put_ioctx(struct kioctx *ctx)
{
      unsigned nr_events = ctx->max_reqs;

      BUG_ON(ctx->reqs_active);

      cancel_delayed_work(&ctx->wq);
      cancel_work_sync(&ctx->wq.work);
      aio_free_ring(ctx);
      mmdrop(ctx->mm);
      ctx->mm = NULL;
      pr_debug("__put_ioctx: freeing %p\n", ctx);
      kmem_cache_free(kioctx_cachep, ctx);

      if (nr_events) {
            spin_lock(&aio_nr_lock);
            BUG_ON(aio_nr - nr_events > aio_nr);
            aio_nr -= nr_events;
            spin_unlock(&aio_nr_lock);
      }
}

/* aio_get_req
 *    Allocate a slot for an aio request.  Increments the users count
 * of the kioctx so that the kioctx stays around until all requests are
 * complete.  Returns NULL if no requests are free.
 *
 * Returns with kiocb->users set to 2.  The io submit code path holds
 * an extra reference while submitting the i/o.
 * This prevents races between the aio code path referencing the
 * req (after submitting it) and aio_complete() freeing the req.
 */
static struct kiocb *FASTCALL(__aio_get_req(struct kioctx *ctx));
static struct kiocb fastcall *__aio_get_req(struct kioctx *ctx)
{
      struct kiocb *req = NULL;
      struct aio_ring *ring;
      int okay = 0;

      req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL);
      if (unlikely(!req))
            return NULL;

      req->ki_flags = 0;
      req->ki_users = 2;
      req->ki_key = 0;
      req->ki_ctx = ctx;
      req->ki_cancel = NULL;
      req->ki_retry = NULL;
      req->ki_dtor = NULL;
      req->private = NULL;
      req->ki_iovec = NULL;
      INIT_LIST_HEAD(&req->ki_run_list);
      req->ki_eventfd = ERR_PTR(-EINVAL);

      /* Check if the completion queue has enough free space to
       * accept an event from this io.
       */
      spin_lock_irq(&ctx->ctx_lock);
      ring = kmap_atomic(ctx->ring_info.ring_pages[0], KM_USER0);
      if (ctx->reqs_active < aio_ring_avail(&ctx->ring_info, ring)) {
            list_add(&req->ki_list, &ctx->active_reqs);
            ctx->reqs_active++;
            okay = 1;
      }
      kunmap_atomic(ring, KM_USER0);
      spin_unlock_irq(&ctx->ctx_lock);

      if (!okay) {
            kmem_cache_free(kiocb_cachep, req);
            req = NULL;
      }

      return req;
}

static inline struct kiocb *aio_get_req(struct kioctx *ctx)
{
      struct kiocb *req;
      /* Handle a potential starvation case -- should be exceedingly rare as 
       * requests will be stuck on fput_head only if the aio_fput_routine is 
       * delayed and the requests were the last user of the struct file.
       */
      req = __aio_get_req(ctx);
      if (unlikely(NULL == req)) {
            aio_fput_routine(NULL);
            req = __aio_get_req(ctx);
      }
      return req;
}

static inline void really_put_req(struct kioctx *ctx, struct kiocb *req)
{
      assert_spin_locked(&ctx->ctx_lock);

      if (!IS_ERR(req->ki_eventfd))
            fput(req->ki_eventfd);
      if (req->ki_dtor)
            req->ki_dtor(req);
      if (req->ki_iovec != &req->ki_inline_vec)
            kfree(req->ki_iovec);
      kmem_cache_free(kiocb_cachep, req);
      ctx->reqs_active--;

      if (unlikely(!ctx->reqs_active && ctx->dead))
            wake_up(&ctx->wait);
}

static void aio_fput_routine(struct work_struct *data)
{
      spin_lock_irq(&fput_lock);
      while (likely(!list_empty(&fput_head))) {
            struct kiocb *req = list_kiocb(fput_head.next);
            struct kioctx *ctx = req->ki_ctx;

            list_del(&req->ki_list);
            spin_unlock_irq(&fput_lock);

            /* Complete the fput */
            __fput(req->ki_filp);

            /* Link the iocb into the context's free list */
            spin_lock_irq(&ctx->ctx_lock);
            really_put_req(ctx, req);
            spin_unlock_irq(&ctx->ctx_lock);

            put_ioctx(ctx);
            spin_lock_irq(&fput_lock);
      }
      spin_unlock_irq(&fput_lock);
}

/* __aio_put_req
 *    Returns true if this put was the last user of the request.
 */
static int __aio_put_req(struct kioctx *ctx, struct kiocb *req)
{
      dprintk(KERN_DEBUG "aio_put(%p): f_count=%d\n",
            req, atomic_read(&req->ki_filp->f_count));

      assert_spin_locked(&ctx->ctx_lock);

      req->ki_users --;
      BUG_ON(req->ki_users < 0);
      if (likely(req->ki_users))
            return 0;
      list_del(&req->ki_list);            /* remove from active_reqs */
      req->ki_cancel = NULL;
      req->ki_retry = NULL;

      /* Must be done under the lock to serialise against cancellation.
       * Call this aio_fput as it duplicates fput via the fput_work.
       */
      if (unlikely(atomic_dec_and_test(&req->ki_filp->f_count))) {
            get_ioctx(ctx);
            spin_lock(&fput_lock);
            list_add(&req->ki_list, &fput_head);
            spin_unlock(&fput_lock);
            queue_work(aio_wq, &fput_work);
      } else
            really_put_req(ctx, req);
      return 1;
}

/* aio_put_req
 *    Returns true if this put was the last user of the kiocb,
 *    false if the request is still in use.
 */
int fastcall aio_put_req(struct kiocb *req)
{
      struct kioctx *ctx = req->ki_ctx;
      int ret;
      spin_lock_irq(&ctx->ctx_lock);
      ret = __aio_put_req(ctx, req);
      spin_unlock_irq(&ctx->ctx_lock);
      return ret;
}

/*    Lookup an ioctx id.  ioctx_list is lockless for reads.
 *    FIXME: this is O(n) and is only suitable for development.
 */
struct kioctx *lookup_ioctx(unsigned long ctx_id)
{
      struct kioctx *ioctx;
      struct mm_struct *mm;

      mm = current->mm;
      read_lock(&mm->ioctx_list_lock);
      for (ioctx = mm->ioctx_list; ioctx; ioctx = ioctx->next)
            if (likely(ioctx->user_id == ctx_id && !ioctx->dead)) {
                  get_ioctx(ioctx);
                  break;
            }
      read_unlock(&mm->ioctx_list_lock);

      return ioctx;
}

/*
 * use_mm
 *    Makes the calling kernel thread take on the specified
 *    mm context.
 *    Called by the retry thread execute retries within the
 *    iocb issuer's mm context, so that copy_from/to_user
 *    operations work seamlessly for aio.
 *    (Note: this routine is intended to be called only
 *    from a kernel thread context)
 */
static void use_mm(struct mm_struct *mm)
{
      struct mm_struct *active_mm;
      struct task_struct *tsk = current;

      task_lock(tsk);
      tsk->flags |= PF_BORROWED_MM;
      active_mm = tsk->active_mm;
      atomic_inc(&mm->mm_count);
      tsk->mm = mm;
      tsk->active_mm = mm;
      /*
       * Note that on UML this *requires* PF_BORROWED_MM to be set, otherwise
       * it won't work. Update it accordingly if you change it here
       */
      switch_mm(active_mm, mm, tsk);
      task_unlock(tsk);

      mmdrop(active_mm);
}

/*
 * unuse_mm
 *    Reverses the effect of use_mm, i.e. releases the
 *    specified mm context which was earlier taken on
 *    by the calling kernel thread
 *    (Note: this routine is intended to be called only
 *    from a kernel thread context)
 */
static void unuse_mm(struct mm_struct *mm)
{
      struct task_struct *tsk = current;

      task_lock(tsk);
      tsk->flags &= ~PF_BORROWED_MM;
      tsk->mm = NULL;
      /* active_mm is still 'mm' */
      enter_lazy_tlb(mm, tsk);
      task_unlock(tsk);
}

/*
 * Queue up a kiocb to be retried. Assumes that the kiocb
 * has already been marked as kicked, and places it on
 * the retry run list for the corresponding ioctx, if it
 * isn't already queued. Returns 1 if it actually queued
 * the kiocb (to tell the caller to activate the work
 * queue to process it), or 0, if it found that it was
 * already queued.
 */
static inline int __queue_kicked_iocb(struct kiocb *iocb)
{
      struct kioctx *ctx = iocb->ki_ctx;

      assert_spin_locked(&ctx->ctx_lock);

      if (list_empty(&iocb->ki_run_list)) {
            list_add_tail(&iocb->ki_run_list,
                  &ctx->run_list);
            return 1;
      }
      return 0;
}

/* aio_run_iocb
 *    This is the core aio execution routine. It is
 *    invoked both for initial i/o submission and
 *    subsequent retries via the aio_kick_handler.
 *    Expects to be invoked with iocb->ki_ctx->lock
 *    already held. The lock is released and reacquired
 *    as needed during processing.
 *
 * Calls the iocb retry method (already setup for the
 * iocb on initial submission) for operation specific
 * handling, but takes care of most of common retry
 * execution details for a given iocb. The retry method
 * needs to be non-blocking as far as possible, to avoid
 * holding up other iocbs waiting to be serviced by the
 * retry kernel thread.
 *
 * The trickier parts in this code have to do with
 * ensuring that only one retry instance is in progress
 * for a given iocb at any time. Providing that guarantee
 * simplifies the coding of individual aio operations as
 * it avoids various potential races.
 */
static ssize_t aio_run_iocb(struct kiocb *iocb)
{
      struct kioctx     *ctx = iocb->ki_ctx;
      ssize_t (*retry)(struct kiocb *);
      ssize_t ret;

      if (!(retry = iocb->ki_retry)) {
            printk("aio_run_iocb: iocb->ki_retry = NULL\n");
            return 0;
      }

      /*
       * We don't want the next retry iteration for this
       * operation to start until this one has returned and
       * updated the iocb state. However, wait_queue functions
       * can trigger a kick_iocb from interrupt context in the
       * meantime, indicating that data is available for the next
       * iteration. We want to remember that and enable the
       * next retry iteration _after_ we are through with
       * this one.
       *
       * So, in order to be able to register a "kick", but
       * prevent it from being queued now, we clear the kick
       * flag, but make the kick code *think* that the iocb is
       * still on the run list until we are actually done.
       * When we are done with this iteration, we check if
       * the iocb was kicked in the meantime and if so, queue
       * it up afresh.
       */

      kiocbClearKicked(iocb);

      /*
       * This is so that aio_complete knows it doesn't need to
       * pull the iocb off the run list (We can't just call
       * INIT_LIST_HEAD because we don't want a kick_iocb to
       * queue this on the run list yet)
       */
      iocb->ki_run_list.next = iocb->ki_run_list.prev = NULL;
      spin_unlock_irq(&ctx->ctx_lock);

      /* Quit retrying if the i/o has been cancelled */
      if (kiocbIsCancelled(iocb)) {
            ret = -EINTR;
            aio_complete(iocb, ret, 0);
            /* must not access the iocb after this */
            goto out;
      }

      /*
       * Now we are all set to call the retry method in async
       * context.
       */
      ret = retry(iocb);

      if (ret != -EIOCBRETRY && ret != -EIOCBQUEUED) {
            BUG_ON(!list_empty(&iocb->ki_wait.task_list));
            aio_complete(iocb, ret, 0);
      }
out:
      spin_lock_irq(&ctx->ctx_lock);

      if (-EIOCBRETRY == ret) {
            /*
             * OK, now that we are done with this iteration
             * and know that there is more left to go,
             * this is where we let go so that a subsequent
             * "kick" can start the next iteration
             */

            /* will make __queue_kicked_iocb succeed from here on */
            INIT_LIST_HEAD(&iocb->ki_run_list);
            /* we must queue the next iteration ourselves, if it
             * has already been kicked */
            if (kiocbIsKicked(iocb)) {
                  __queue_kicked_iocb(iocb);

                  /*
                   * __queue_kicked_iocb will always return 1 here, because
                   * iocb->ki_run_list is empty at this point so it should
                   * be safe to unconditionally queue the context into the
                   * work queue.
                   */
                  aio_queue_work(ctx);
            }
      }
      return ret;
}

/*
 * __aio_run_iocbs:
 *    Process all pending retries queued on the ioctx
 *    run list.
 * Assumes it is operating within the aio issuer's mm
 * context.
 */
static int __aio_run_iocbs(struct kioctx *ctx)
{
      struct kiocb *iocb;
      struct list_head run_list;

      assert_spin_locked(&ctx->ctx_lock);

      list_replace_init(&ctx->run_list, &run_list);
      while (!list_empty(&run_list)) {
            iocb = list_entry(run_list.next, struct kiocb,
                  ki_run_list);
            list_del(&iocb->ki_run_list);
            /*
             * Hold an extra reference while retrying i/o.
             */
            iocb->ki_users++;       /* grab extra reference */
            aio_run_iocb(iocb);
            __aio_put_req(ctx, iocb);
      }
      if (!list_empty(&ctx->run_list))
            return 1;
      return 0;
}

static void aio_queue_work(struct kioctx * ctx)
{
      unsigned long timeout;
      /*
       * if someone is waiting, get the work started right
       * away, otherwise, use a longer delay
       */
      smp_mb();
      if (waitqueue_active(&ctx->wait))
            timeout = 1;
      else
            timeout = HZ/10;
      queue_delayed_work(aio_wq, &ctx->wq, timeout);
}


/*
 * aio_run_iocbs:
 *    Process all pending retries queued on the ioctx
 *    run list.
 * Assumes it is operating within the aio issuer's mm
 * context.
 */
static inline void aio_run_iocbs(struct kioctx *ctx)
{
      int requeue;

      spin_lock_irq(&ctx->ctx_lock);

      requeue = __aio_run_iocbs(ctx);
      spin_unlock_irq(&ctx->ctx_lock);
      if (requeue)
            aio_queue_work(ctx);
}

/*
 * just like aio_run_iocbs, but keeps running them until
 * the list stays empty
 */
static inline void aio_run_all_iocbs(struct kioctx *ctx)
{
      spin_lock_irq(&ctx->ctx_lock);
      while (__aio_run_iocbs(ctx))
            ;
      spin_unlock_irq(&ctx->ctx_lock);
}

/*
 * aio_kick_handler:
 *    Work queue handler triggered to process pending
 *    retries on an ioctx. Takes on the aio issuer's
 *    mm context before running the iocbs, so that
 *    copy_xxx_user operates on the issuer's address
 *      space.
 * Run on aiod's context.
 */
static void aio_kick_handler(struct work_struct *work)
{
      struct kioctx *ctx = container_of(work, struct kioctx, wq.work);
      mm_segment_t oldfs = get_fs();
      struct mm_struct *mm;
      int requeue;

      set_fs(USER_DS);
      use_mm(ctx->mm);
      spin_lock_irq(&ctx->ctx_lock);
      requeue =__aio_run_iocbs(ctx);
      mm = ctx->mm;
      spin_unlock_irq(&ctx->ctx_lock);
      unuse_mm(mm);
      set_fs(oldfs);
      /*
       * we're in a worker thread already, don't use queue_delayed_work,
       */
      if (requeue)
            queue_delayed_work(aio_wq, &ctx->wq, 0);
}


/*
 * Called by kick_iocb to queue the kiocb for retry
 * and if required activate the aio work queue to process
 * it
 */
static void try_queue_kicked_iocb(struct kiocb *iocb)
{
      struct kioctx     *ctx = iocb->ki_ctx;
      unsigned long flags;
      int run = 0;

      /* We're supposed to be the only path putting the iocb back on the run
       * list.  If we find that the iocb is *back* on a wait queue already
       * than retry has happened before we could queue the iocb.  This also
       * means that the retry could have completed and freed our iocb, no
       * good. */
      BUG_ON((!list_empty(&iocb->ki_wait.task_list)));

      spin_lock_irqsave(&ctx->ctx_lock, flags);
      /* set this inside the lock so that we can't race with aio_run_iocb()
       * testing it and putting the iocb on the run list under the lock */
      if (!kiocbTryKick(iocb))
            run = __queue_kicked_iocb(iocb);
      spin_unlock_irqrestore(&ctx->ctx_lock, flags);
      if (run)
            aio_queue_work(ctx);
}

/*
 * kick_iocb:
 *      Called typically from a wait queue callback context
 *      (aio_wake_function) to trigger a retry of the iocb.
 *      The retry is usually executed by aio workqueue
 *      threads (See aio_kick_handler).
 */
void fastcall kick_iocb(struct kiocb *iocb)
{
      /* sync iocbs are easy: they can only ever be executing from a 
       * single context. */
      if (is_sync_kiocb(iocb)) {
            kiocbSetKicked(iocb);
              wake_up_process(iocb->ki_obj.tsk);
            return;
      }

      try_queue_kicked_iocb(iocb);
}
EXPORT_SYMBOL(kick_iocb);

/* aio_complete
 *    Called when the io request on the given iocb is complete.
 *    Returns true if this is the last user of the request.  The 
 *    only other user of the request can be the cancellation code.
 */
int fastcall aio_complete(struct kiocb *iocb, long res, long res2)
{
      struct kioctx     *ctx = iocb->ki_ctx;
      struct aio_ring_info    *info;
      struct aio_ring   *ring;
      struct io_event   *event;
      unsigned long     flags;
      unsigned long     tail;
      int         ret;

      /*
       * Special case handling for sync iocbs:
       *  - events go directly into the iocb for fast handling
       *  - the sync task with the iocb in its stack holds the single iocb
       *    ref, no other paths have a way to get another ref
       *  - the sync task helpfully left a reference to itself in the iocb
       */
      if (is_sync_kiocb(iocb)) {
            BUG_ON(iocb->ki_users != 1);
            iocb->ki_user_data = res;
            iocb->ki_users = 0;
            wake_up_process(iocb->ki_obj.tsk);
            return 1;
      }

      /*
       * Check if the user asked us to deliver the result through an
       * eventfd. The eventfd_signal() function is safe to be called
       * from IRQ context.
       */
      if (!IS_ERR(iocb->ki_eventfd))
            eventfd_signal(iocb->ki_eventfd, 1);

      info = &ctx->ring_info;

      /* add a completion event to the ring buffer.
       * must be done holding ctx->ctx_lock to prevent
       * other code from messing with the tail
       * pointer since we might be called from irq
       * context.
       */
      spin_lock_irqsave(&ctx->ctx_lock, flags);

      if (iocb->ki_run_list.prev && !list_empty(&iocb->ki_run_list))
            list_del_init(&iocb->ki_run_list);

      /*
       * cancelled requests don't get events, userland was given one
       * when the event got cancelled.
       */
      if (kiocbIsCancelled(iocb))
            goto put_rq;

      ring = kmap_atomic(info->ring_pages[0], KM_IRQ1);

      tail = info->tail;
      event = aio_ring_event(info, tail, KM_IRQ0);
      if (++tail >= info->nr)
            tail = 0;

      event->obj = (u64)(unsigned long)iocb->ki_obj.user;
      event->data = iocb->ki_user_data;
      event->res = res;
      event->res2 = res2;

      dprintk("aio_complete: %p[%lu]: %p: %p %Lx %lx %lx\n",
            ctx, tail, iocb, iocb->ki_obj.user, iocb->ki_user_data,
            res, res2);

      /* after flagging the request as done, we
       * must never even look at it again
       */
      smp_wmb();  /* make event visible before updating tail */

      info->tail = tail;
      ring->tail = tail;

      put_aio_ring_event(event, KM_IRQ0);
      kunmap_atomic(ring, KM_IRQ1);

      pr_debug("added to ring %p at [%lu]\n", iocb, tail);
put_rq:
      /* everything turned out well, dispose of the aiocb. */
      ret = __aio_put_req(ctx, iocb);

      if (waitqueue_active(&ctx->wait))
            wake_up(&ctx->wait);

      spin_unlock_irqrestore(&ctx->ctx_lock, flags);
      return ret;
}

/* aio_read_evt
 *    Pull an event off of the ioctx's event ring.  Returns the number of 
 *    events fetched (0 or 1 ;-)
 *    FIXME: make this use cmpxchg.
 *    TODO: make the ringbuffer user mmap()able (requires FIXME).
 */
static int aio_read_evt(struct kioctx *ioctx, struct io_event *ent)
{
      struct aio_ring_info *info = &ioctx->ring_info;
      struct aio_ring *ring;
      unsigned long head;
      int ret = 0;

      ring = kmap_atomic(info->ring_pages[0], KM_USER0);
      dprintk("in aio_read_evt h%lu t%lu m%lu\n",
             (unsigned long)ring->head, (unsigned long)ring->tail,
             (unsigned long)ring->nr);

      if (ring->head == ring->tail)
            goto out;

      spin_lock(&info->ring_lock);

      head = ring->head % info->nr;
      if (head != ring->tail) {
            struct io_event *evp = aio_ring_event(info, head, KM_USER1);
            *ent = *evp;
            head = (head + 1) % info->nr;
            smp_mb(); /* finish reading the event before updatng the head */
            ring->head = head;
            ret = 1;
            put_aio_ring_event(evp, KM_USER1);
      }
      spin_unlock(&info->ring_lock);

out:
      kunmap_atomic(ring, KM_USER0);
      dprintk("leaving aio_read_evt: %d  h%lu t%lu\n", ret,
             (unsigned long)ring->head, (unsigned long)ring->tail);
      return ret;
}

struct aio_timeout {
      struct timer_list timer;
      int               timed_out;
      struct task_struct      *p;
};

static void timeout_func(unsigned long data)
{
      struct aio_timeout *to = (struct aio_timeout *)data;

      to->timed_out = 1;
      wake_up_process(to->p);
}

static inline void init_timeout(struct aio_timeout *to)
{
      init_timer(&to->timer);
      to->timer.data = (unsigned long)to;
      to->timer.function = timeout_func;
      to->timed_out = 0;
      to->p = current;
}

static inline void set_timeout(long start_jiffies, struct aio_timeout *to,
                         const struct timespec *ts)
{
      to->timer.expires = start_jiffies + timespec_to_jiffies(ts);
      if (time_after(to->timer.expires, jiffies))
            add_timer(&to->timer);
      else
            to->timed_out = 1;
}

static inline void clear_timeout(struct aio_timeout *to)
{
      del_singleshot_timer_sync(&to->timer);
}

static int read_events(struct kioctx *ctx,
                  long min_nr, long nr,
                  struct io_event __user *event,
                  struct timespec __user *timeout)
{
      long              start_jiffies = jiffies;
      struct task_struct      *tsk = current;
      DECLARE_WAITQUEUE(wait, tsk);
      int               ret;
      int               i = 0;
      struct io_event         ent;
      struct aio_timeout      to;
      int               retry = 0;

      /* needed to zero any padding within an entry (there shouldn't be 
       * any, but C is fun!
       */
      memset(&ent, 0, sizeof(ent));
retry:
      ret = 0;
      while (likely(i < nr)) {
            ret = aio_read_evt(ctx, &ent);
            if (unlikely(ret <= 0))
                  break;

            dprintk("read event: %Lx %Lx %Lx %Lx\n",
                  ent.data, ent.obj, ent.res, ent.res2);

            /* Could we split the check in two? */
            ret = -EFAULT;
            if (unlikely(copy_to_user(event, &ent, sizeof(ent)))) {
                  dprintk("aio: lost an event due to EFAULT.\n");
                  break;
            }
            ret = 0;

            /* Good, event copied to userland, update counts. */
            event ++;
            i ++;
      }

      if (min_nr <= i)
            return i;
      if (ret)
            return ret;

      /* End fast path */

      /* racey check, but it gets redone */
      if (!retry && unlikely(!list_empty(&ctx->run_list))) {
            retry = 1;
            aio_run_all_iocbs(ctx);
            goto retry;
      }

      init_timeout(&to);
      if (timeout) {
            struct timespec   ts;
            ret = -EFAULT;
            if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
                  goto out;

            set_timeout(start_jiffies, &to, &ts);
      }

      while (likely(i < nr)) {
            add_wait_queue_exclusive(&ctx->wait, &wait);
            do {
                  set_task_state(tsk, TASK_INTERRUPTIBLE);
                  ret = aio_read_evt(ctx, &ent);
                  if (ret)
                        break;
                  if (min_nr <= i)
                        break;
                  ret = 0;
                  if (to.timed_out) /* Only check after read evt */
                        break;
                  /* Try to only show up in io wait if there are ops
                   *  in flight */
                  if (ctx->reqs_active)
                        io_schedule();
                  else
                        schedule();
                  if (signal_pending(tsk)) {
                        ret = -EINTR;
                        break;
                  }
                  /*ret = aio_read_evt(ctx, &ent);*/
            } while (1) ;

            set_task_state(tsk, TASK_RUNNING);
            remove_wait_queue(&ctx->wait, &wait);

            if (unlikely(ret <= 0))
                  break;

            ret = -EFAULT;
            if (unlikely(copy_to_user(event, &ent, sizeof(ent)))) {
                  dprintk("aio: lost an event due to EFAULT.\n");
                  break;
            }

            /* Good, event copied to userland, update counts. */
            event ++;
            i ++;
      }

      if (timeout)
            clear_timeout(&to);
out:
      return i ? i : ret;
}

/* Take an ioctx and remove it from the list of ioctx's.  Protects 
 * against races with itself via ->dead.
 */
static void io_destroy(struct kioctx *ioctx)
{
      struct mm_struct *mm = current->mm;
      struct kioctx **tmp;
      int was_dead;

      /* delete the entry from the list is someone else hasn't already */
      write_lock(&mm->ioctx_list_lock);
      was_dead = ioctx->dead;
      ioctx->dead = 1;
      for (tmp = &mm->ioctx_list; *tmp && *tmp != ioctx;
           tmp = &(*tmp)->next)
            ;
      if (*tmp)
            *tmp = ioctx->next;
      write_unlock(&mm->ioctx_list_lock);

      dprintk("aio_release(%p)\n", ioctx);
      if (likely(!was_dead))
            put_ioctx(ioctx); /* twice for the list */

      aio_cancel_all(ioctx);
      wait_for_all_aios(ioctx);
      put_ioctx(ioctx); /* once for the lookup */
}

/* sys_io_setup:
 *    Create an aio_context capable of receiving at least nr_events.
 *    ctxp must not point to an aio_context that already exists, and
 *    must be initialized to 0 prior to the call.  On successful
 *    creation of the aio_context, *ctxp is filled in with the resulting 
 *    handle.  May fail with -EINVAL if *ctxp is not initialized,
 *    if the specified nr_events exceeds internal limits.  May fail 
 *    with -EAGAIN if the specified nr_events exceeds the user's limit 
 *    of available events.  May fail with -ENOMEM if insufficient kernel
 *    resources are available.  May fail with -EFAULT if an invalid
 *    pointer is passed for ctxp.  Will fail with -ENOSYS if not
 *    implemented.
 */
asmlinkage long sys_io_setup(unsigned nr_events, aio_context_t __user *ctxp)
{
      struct kioctx *ioctx = NULL;
      unsigned long ctx;
      long ret;

      ret = get_user(ctx, ctxp);
      if (unlikely(ret))
            goto out;

      ret = -EINVAL;
      if (unlikely(ctx || nr_events == 0)) {
            pr_debug("EINVAL: io_setup: ctx %lu nr_events %u\n",
                     ctx, nr_events);
            goto out;
      }

      ioctx = ioctx_alloc(nr_events);
      ret = PTR_ERR(ioctx);
      if (!IS_ERR(ioctx)) {
            ret = put_user(ioctx->user_id, ctxp);
            if (!ret)
                  return 0;

            get_ioctx(ioctx); /* io_destroy() expects us to hold a ref */
            io_destroy(ioctx);
      }

out:
      return ret;
}

/* sys_io_destroy:
 *    Destroy the aio_context specified.  May cancel any outstanding 
 *    AIOs and block on completion.  Will fail with -ENOSYS if not
 *    implemented.  May fail with -EFAULT if the context pointed to
 *    is invalid.
 */
asmlinkage long sys_io_destroy(aio_context_t ctx)
{
      struct kioctx *ioctx = lookup_ioctx(ctx);
      if (likely(NULL != ioctx)) {
            io_destroy(ioctx);
            return 0;
      }
      pr_debug("EINVAL: io_destroy: invalid context id\n");
      return -EINVAL;
}

static void aio_advance_iovec(struct kiocb *iocb, ssize_t ret)
{
      struct iovec *iov = &iocb->ki_iovec[iocb->ki_cur_seg];

      BUG_ON(ret <= 0);

      while (iocb->ki_cur_seg < iocb->ki_nr_segs && ret > 0) {
            ssize_t this = min((ssize_t)iov->iov_len, ret);
            iov->iov_base += this;
            iov->iov_len -= this;
            iocb->ki_left -= this;
            ret -= this;
            if (iov->iov_len == 0) {
                  iocb->ki_cur_seg++;
                  iov++;
            }
      }

      /* the caller should not have done more io than what fit in
       * the remaining iovecs */
      BUG_ON(ret > 0 && iocb->ki_left == 0);
}

static ssize_t aio_rw_vect_retry(struct kiocb *iocb)
{
      struct file *file = iocb->ki_filp;
      struct address_space *mapping = file->f_mapping;
      struct inode *inode = mapping->host;
      ssize_t (*rw_op)(struct kiocb *, const struct iovec *,
                   unsigned long, loff_t);
      ssize_t ret = 0;
      unsigned short opcode;

      if ((iocb->ki_opcode == IOCB_CMD_PREADV) ||
            (iocb->ki_opcode == IOCB_CMD_PREAD)) {
            rw_op = file->f_op->aio_read;
            opcode = IOCB_CMD_PREADV;
      } else {
            rw_op = file->f_op->aio_write;
            opcode = IOCB_CMD_PWRITEV;
      }

      do {
            ret = rw_op(iocb, &iocb->ki_iovec[iocb->ki_cur_seg],
                      iocb->ki_nr_segs - iocb->ki_cur_seg,
                      iocb->ki_pos);
            if (ret > 0)
                  aio_advance_iovec(iocb, ret);

      /* retry all partial writes.  retry partial reads as long as its a
       * regular file. */
      } while (ret > 0 && iocb->ki_left > 0 &&
             (opcode == IOCB_CMD_PWRITEV ||
              (!S_ISFIFO(inode->i_mode) && !S_ISSOCK(inode->i_mode))));

      /* This means we must have transferred all that we could */
      /* No need to retry anymore */
      if ((ret == 0) || (iocb->ki_left == 0))
            ret = iocb->ki_nbytes - iocb->ki_left;

      return ret;
}

static ssize_t aio_fdsync(struct kiocb *iocb)
{
      struct file *file = iocb->ki_filp;
      ssize_t ret = -EINVAL;

      if (file->f_op->aio_fsync)
            ret = file->f_op->aio_fsync(iocb, 1);
      return ret;
}

static ssize_t aio_fsync(struct kiocb *iocb)
{
      struct file *file = iocb->ki_filp;
      ssize_t ret = -EINVAL;

      if (file->f_op->aio_fsync)
            ret = file->f_op->aio_fsync(iocb, 0);
      return ret;
}

static ssize_t aio_setup_vectored_rw(int type, struct kiocb *kiocb)
{
      ssize_t ret;

      ret = rw_copy_check_uvector(type, (struct iovec __user *)kiocb->ki_buf,
                            kiocb->ki_nbytes, 1,
                            &kiocb->ki_inline_vec, &kiocb->ki_iovec);
      if (ret < 0)
            goto out;

      kiocb->ki_nr_segs = kiocb->ki_nbytes;
      kiocb->ki_cur_seg = 0;
      /* ki_nbytes/left now reflect bytes instead of segs */
      kiocb->ki_nbytes = ret;
      kiocb->ki_left = ret;

      ret = 0;
out:
      return ret;
}

static ssize_t aio_setup_single_vector(struct kiocb *kiocb)
{
      kiocb->ki_iovec = &kiocb->ki_inline_vec;
      kiocb->ki_iovec->iov_base = kiocb->ki_buf;
      kiocb->ki_iovec->iov_len = kiocb->ki_left;
      kiocb->ki_nr_segs = 1;
      kiocb->ki_cur_seg = 0;
      return 0;
}

/*
 * aio_setup_iocb:
 *    Performs the initial checks and aio retry method
 *    setup for the kiocb at the time of io submission.
 */
static ssize_t aio_setup_iocb(struct kiocb *kiocb)
{
      struct file *file = kiocb->ki_filp;
      ssize_t ret = 0;

      switch (kiocb->ki_opcode) {
      case IOCB_CMD_PREAD:
            ret = -EBADF;
            if (unlikely(!(file->f_mode & FMODE_READ)))
                  break;
            ret = -EFAULT;
            if (unlikely(!access_ok(VERIFY_WRITE, kiocb->ki_buf,
                  kiocb->ki_left)))
                  break;
            ret = security_file_permission(file, MAY_READ);
            if (unlikely(ret))
                  break;
            ret = aio_setup_single_vector(kiocb);
            if (ret)
                  break;
            ret = -EINVAL;
            if (file->f_op->aio_read)
                  kiocb->ki_retry = aio_rw_vect_retry;
            break;
      case IOCB_CMD_PWRITE:
            ret = -EBADF;
            if (unlikely(!(file->f_mode & FMODE_WRITE)))
                  break;
            ret = -EFAULT;
            if (unlikely(!access_ok(VERIFY_READ, kiocb->ki_buf,
                  kiocb->ki_left)))
                  break;
            ret = security_file_permission(file, MAY_WRITE);
            if (unlikely(ret))
                  break;
            ret = aio_setup_single_vector(kiocb);
            if (ret)
                  break;
            ret = -EINVAL;
            if (file->f_op->aio_write)
                  kiocb->ki_retry = aio_rw_vect_retry;
            break;
      case IOCB_CMD_PREADV:
            ret = -EBADF;
            if (unlikely(!(file->f_mode & FMODE_READ)))
                  break;
            ret = security_file_permission(file, MAY_READ);
            if (unlikely(ret))
                  break;
            ret = aio_setup_vectored_rw(READ, kiocb);
            if (ret)
                  break;
            ret = -EINVAL;
            if (file->f_op->aio_read)
                  kiocb->ki_retry = aio_rw_vect_retry;
            break;
      case IOCB_CMD_PWRITEV:
            ret = -EBADF;
            if (unlikely(!(file->f_mode & FMODE_WRITE)))
                  break;
            ret = security_file_permission(file, MAY_WRITE);
            if (unlikely(ret))
                  break;
            ret = aio_setup_vectored_rw(WRITE, kiocb);
            if (ret)
                  break;
            ret = -EINVAL;
            if (file->f_op->aio_write)
                  kiocb->ki_retry = aio_rw_vect_retry;
            break;
      case IOCB_CMD_FDSYNC:
            ret = -EINVAL;
            if (file->f_op->aio_fsync)
                  kiocb->ki_retry = aio_fdsync;
            break;
      case IOCB_CMD_FSYNC:
            ret = -EINVAL;
            if (file->f_op->aio_fsync)
                  kiocb->ki_retry = aio_fsync;
            break;
      default:
            dprintk("EINVAL: io_submit: no operation provided\n");
            ret = -EINVAL;
      }

      if (!kiocb->ki_retry)
            return ret;

      return 0;
}

/*
 * aio_wake_function:
 *    wait queue callback function for aio notification,
 *    Simply triggers a retry of the operation via kick_iocb.
 *
 *    This callback is specified in the wait queue entry in
 *    a kiocb.
 *
 * Note:
 * This routine is executed with the wait queue lock held.
 * Since kick_iocb acquires iocb->ctx->ctx_lock, it nests
 * the ioctx lock inside the wait queue lock. This is safe
 * because this callback isn't used for wait queues which
 * are nested inside ioctx lock (i.e. ctx->wait)
 */
static int aio_wake_function(wait_queue_t *wait, unsigned mode,
                       int sync, void *key)
{
      struct kiocb *iocb = container_of(wait, struct kiocb, ki_wait);

      list_del_init(&wait->task_list);
      kick_iocb(iocb);
      return 1;
}

int fastcall io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
                   struct iocb *iocb)
{
      struct kiocb *req;
      struct file *file;
      ssize_t ret;

      /* enforce forwards compatibility on users */
      if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
            pr_debug("EINVAL: io_submit: reserve field set\n");
            return -EINVAL;
      }

      /* prevent overflows */
      if (unlikely(
          (iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
          (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
          ((ssize_t)iocb->aio_nbytes < 0)
         )) {
            pr_debug("EINVAL: io_submit: overflow check\n");
            return -EINVAL;
      }

      file = fget(iocb->aio_fildes);
      if (unlikely(!file))
            return -EBADF;

      req = aio_get_req(ctx);       /* returns with 2 references to req */
      if (unlikely(!req)) {
            fput(file);
            return -EAGAIN;
      }
      req->ki_filp = file;
      if (iocb->aio_flags & IOCB_FLAG_RESFD) {
            /*
             * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
             * instance of the file* now. The file descriptor must be
             * an eventfd() fd, and will be signaled for each completed
             * event using the eventfd_signal() function.
             */
            req->ki_eventfd = eventfd_fget((int) iocb->aio_resfd);
            if (unlikely(IS_ERR(req->ki_eventfd))) {
                  ret = PTR_ERR(req->ki_eventfd);
                  goto out_put_req;
            }
      }

      ret = put_user(req->ki_key, &user_iocb->aio_key);
      if (unlikely(ret)) {
            dprintk("EFAULT: aio_key\n");
            goto out_put_req;
      }

      req->ki_obj.user = user_iocb;
      req->ki_user_data = iocb->aio_data;
      req->ki_pos = iocb->aio_offset;

      req->ki_buf = (char __user *)(unsigned long)iocb->aio_buf;
      req->ki_left = req->ki_nbytes = iocb->aio_nbytes;
      req->ki_opcode = iocb->aio_lio_opcode;
      init_waitqueue_func_entry(&req->ki_wait, aio_wake_function);
      INIT_LIST_HEAD(&req->ki_wait.task_list);

      ret = aio_setup_iocb(req);

      if (ret)
            goto out_put_req;

      spin_lock_irq(&ctx->ctx_lock);
      aio_run_iocb(req);
      if (!list_empty(&ctx->run_list)) {
            /* drain the run list */
            while (__aio_run_iocbs(ctx))
                  ;
      }
      spin_unlock_irq(&ctx->ctx_lock);
      aio_put_req(req); /* drop extra ref to req */
      return 0;

out_put_req:
      aio_put_req(req); /* drop extra ref to req */
      aio_put_req(req); /* drop i/o ref to req */
      return ret;
}

/* sys_io_submit:
 *    Queue the nr iocbs pointed to by iocbpp for processing.  Returns
 *    the number of iocbs queued.  May return -EINVAL if the aio_context
 *    specified by ctx_id is invalid, if nr is < 0, if the iocb at
 *    *iocbpp[0] is not properly initialized, if the operation specified
 *    is invalid for the file descriptor in the iocb.  May fail with
 *    -EFAULT if any of the data structures point to invalid data.  May
 *    fail with -EBADF if the file descriptor specified in the first
 *    iocb is invalid.  May fail with -EAGAIN if insufficient resources
 *    are available to queue any iocbs.  Will return 0 if nr is 0.  Will
 *    fail with -ENOSYS if not implemented.
 */
asmlinkage long sys_io_submit(aio_context_t ctx_id, long nr,
                        struct iocb __user * __user *iocbpp)
{
      struct kioctx *ctx;
      long ret = 0;
      int i;

      if (unlikely(nr < 0))
            return -EINVAL;

      if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
            return -EFAULT;

      ctx = lookup_ioctx(ctx_id);
      if (unlikely(!ctx)) {
            pr_debug("EINVAL: io_submit: invalid context id\n");
            return -EINVAL;
      }

      /*
       * AKPM: should this return a partial result if some of the IOs were
       * successfully submitted?
       */
      for (i=0; i<nr; i++) {
            struct iocb __user *user_iocb;
            struct iocb tmp;

            if (unlikely(__get_user(user_iocb, iocbpp + i))) {
                  ret = -EFAULT;
                  break;
            }

            if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
                  ret = -EFAULT;
                  break;
            }

            ret = io_submit_one(ctx, user_iocb, &tmp);
            if (ret)
                  break;
      }

      put_ioctx(ctx);
      return i ? i : ret;
}

/* lookup_kiocb
 *    Finds a given iocb for cancellation.
 */
static struct kiocb *lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb,
                          u32 key)
{
      struct list_head *pos;

      assert_spin_locked(&ctx->ctx_lock);

      /* TODO: use a hash or array, this sucks. */
      list_for_each(pos, &ctx->active_reqs) {
            struct kiocb *kiocb = list_kiocb(pos);
            if (kiocb->ki_obj.user == iocb && kiocb->ki_key == key)
                  return kiocb;
      }
      return NULL;
}

/* sys_io_cancel:
 *    Attempts to cancel an iocb previously passed to io_submit.  If
 *    the operation is successfully cancelled, the resulting event is
 *    copied into the memory pointed to by result without being placed
 *    into the completion queue and 0 is returned.  May fail with
 *    -EFAULT if any of the data structures pointed to are invalid.
 *    May fail with -EINVAL if aio_context specified by ctx_id is
 *    invalid.  May fail with -EAGAIN if the iocb specified was not
 *    cancelled.  Will fail with -ENOSYS if not implemented.
 */
asmlinkage long sys_io_cancel(aio_context_t ctx_id, struct iocb __user *iocb,
                        struct io_event __user *result)
{
      int (*cancel)(struct kiocb *iocb, struct io_event *res);
      struct kioctx *ctx;
      struct kiocb *kiocb;
      u32 key;
      int ret;

      ret = get_user(key, &iocb->aio_key);
      if (unlikely(ret))
            return -EFAULT;

      ctx = lookup_ioctx(ctx_id);
      if (unlikely(!ctx))
            return -EINVAL;

      spin_lock_irq(&ctx->ctx_lock);
      ret = -EAGAIN;
      kiocb = lookup_kiocb(ctx, iocb, key);
      if (kiocb && kiocb->ki_cancel) {
            cancel = kiocb->ki_cancel;
            kiocb->ki_users ++;
            kiocbSetCancelled(kiocb);
      } else
            cancel = NULL;
      spin_unlock_irq(&ctx->ctx_lock);

      if (NULL != cancel) {
            struct io_event tmp;
            pr_debug("calling cancel\n");
            memset(&tmp, 0, sizeof(tmp));
            tmp.obj = (u64)(unsigned long)kiocb->ki_obj.user;
            tmp.data = kiocb->ki_user_data;
            ret = cancel(kiocb, &tmp);
            if (!ret) {
                  /* Cancellation succeeded -- copy the result
                   * into the user's buffer.
                   */
                  if (copy_to_user(result, &tmp, sizeof(tmp)))
                        ret = -EFAULT;
            }
      } else
            ret = -EINVAL;

      put_ioctx(ctx);

      return ret;
}

/* io_getevents:
 *    Attempts to read at least min_nr events and up to nr events from
 *    the completion queue for the aio_context specified by ctx_id.  May
 *    fail with -EINVAL if ctx_id is invalid, if min_nr is out of range,
 *    if nr is out of range, if when is out of range.  May fail with
 *    -EFAULT if any of the memory specified to is invalid.  May return
 *    0 or < min_nr if no events are available and the timeout specified
 *    by when     has elapsed, where when == NULL specifies an infinite
 *    timeout.  Note that the timeout pointed to by when is relative and
 *    will be updated if not NULL and the operation blocks.  Will fail
 *    with -ENOSYS if not implemented.
 */
asmlinkage long sys_io_getevents(aio_context_t ctx_id,
                         long min_nr,
                         long nr,
                         struct io_event __user *events,
                         struct timespec __user *timeout)
{
      struct kioctx *ioctx = lookup_ioctx(ctx_id);
      long ret = -EINVAL;

      if (likely(ioctx)) {
            if (likely(min_nr <= nr && min_nr >= 0 && nr >= 0))
                  ret = read_events(ioctx, min_nr, nr, events, timeout);
            put_ioctx(ioctx);
      }

      return ret;
}

__initcall(aio_setup);

EXPORT_SYMBOL(aio_complete);
EXPORT_SYMBOL(aio_put_req);
EXPORT_SYMBOL(wait_on_sync_kiocb);

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